Process for the biological production of citric acid



Patented Apr. 24, 951 2,550,243

PROCESS FOR THE BIOLOGICAL PRODUC- TION OF CITRIC ACID Evert H. Groot, Amsterdam, Netherlands, as-

signor to Naamlooze Vennootschap: W. A. Scholtens Aardappelmeelfabrieken, Groningen, Netherlands, a corporation of the Netherlands N Drawing. Application August 11, 1947, Serial Ago. 768,083. In the Netherlands October 2, 1' 45 Section 1, Public Law 690, August 8, 1946 Patent expires October 2, 1965 5 Claims. (01. 195-36) 1 z It has already been known to produce citric acid citric acid formed in the various tests were as from carbohydrates, and particularly from sacfollows: charose by biological processes. A micro-organism which is particularly suited for the purpose Extractadded Citric acid Pet is Aspergil lus nigenaqcording to Perquin (Disser- 5 Cent tation, Delft, 1938) Thus, citric acid may be prepared by cultivating the micro-organisms capanone averagnw ble of producing citric acid in a sugar solution 4 containing the required nutrient inorganic salts, and recovering the resulting citric acid in a p sugar beets average 2.95 {3: average 3.05

' known way from the fermented lIl red beets average3.65

'It has now been found according to the present invention that the said process may be materially improved and increased yields of citric acid may be obtained, by cultivating micro-organisms capable of producing citric acid in a sugar solution which in addition to the usual mineral substances required for theibiological conversion, also contains the material of the tuberous roots of plants Extract added Citric acid, Per of Beta and/or Brassica species, the said material being preferably incorporated with the nutri- 1 1 cut liquid in the form of an aqueous extract. It 110119 averagel.5 has been experienced most surprisingly that in Sugar beets average In the following series of tests also 1:2.5 extracts were used, whereas the total cultivation period amounted to '7 days. The amounts of citric acid formed were as follows:

conse uence of the said addition the amount of 8.5 citric icid formed in the time unit is considerably humps 8.3} average increased. The extract of red beets was found red beets 11.8. average 11.8 to be particularly suitable for the purpose, al- 7 though good results were also obtained with ex- As may appear from these tests, sugar beet tracts of Sugar beets and turnipsand turnip extracts have substantially the same The efiect 0f the process according the stimulating eifect on the citric acidproduction, Vention may further appeal from the results of whereas the red beet extract has a definitely a series of tests with Aspergzllus nzger cultivated Stronger effect in nutrient liquids of the following composition: It is not known with certainty to which ponents of the said vegetable materials the stimulating effect is to be attributed. However, it was medmmA medmm B found advantageous to peel the sugar beets be- 14% 14% fore preparing the extract, as the peel seems to ggollzlngzg/lggocirl n. 1 1 cici ntaintsomef iirilbstatnces wliiizfzh counteract the 5 s mm a ion 0 e 01 me am orma ion.

Mg SOUHO mm 100 25 mm 100 40 While it may generally be preferred to add the extracts of the roots of Beta and Brassica species The initial pH of the liquid was 4.0. to the nutrient solution used for the cultivation The extracts of the ro t W p p d y of the micro-organisms capable of producing treating the raw material with distilled water citric acid, satisfactory results may also be at 70 C. for about 1 ho filtering the mass achieved by adding the material of the tuberous through a suction filter, and sterilizin h filroots itself in a more or less finely divided contrate. Sugar beets were used in peeled conditio dition to the nutrient solution, although in the The first series of tests were carried out with latter way the improvement of the yield of citric the use of extracts prepared by treating one part id may b less striking, by weight of sugar beets, turnips or red beets I claim:

With parts y W i ht of Water as above 1. Aprocess of producing citric acid, which com- Scribed, a d adding 50 C1113 of extract 011 h prises cultivating a mold of the Aspergillus group 100 cm. of the above tabulated nutrient liquids. in a nutrient medium consisting of a sugar solu- The cu tiva g Period Was 6 yd all tests tion containing 14% of saccharose in addition to were carried out in duplicate The amounts of the inorganic salts required in a nutrient medium, to which nutrient medium an aqueous extract of red beets has been added a proportion of about 0.50' liter of an extract of 1 part by weight of the tuberous root with about 2 /2 parts by weight of Water, per liter of nutrient medium.

2. A process of producing citric acid, which comprises cultivating a mold of the Aspergillus. group in a nutrient medium consisting of a sugar solution containing 14% of saccharose in addition to the inorganic salts required in a nutrient medium, to which nutrient medium an aqueous extract of a tuberous root of a plant of the Beta species has been added in a proportion of about 0.50 liter of an extract of 1 part by weight of the tuberous root with about 2 parts by weight of water, per liter of nutrient medium.

3. A process of producing citric acid, which comprises cultivating Aspergillus niger in a nutrient medium consisting of a sugar solution containing 14% of saccharose in addition to the inorganic salts required in a nutrient medium, to which nutrient medium an aqueous extract of a tuberous root of a plant of the Beta species has been added in a proportion of about 0.50 liter of an extract of 1 part by weight of the tuberous root with about 2 parts by weight of water, per liter of nutrient medium.

4. A process of producing citric acid, which comprises cultivating Aspergillus niger in a nutrient medium consisting of a sugar solution containing 14% of saccharose in addition to the inorganic salts required in a nutrient medium, to

which nutrient medium an aqueous extract of red beets has been added in a, proportion of about 0.50' liter of an extract of 1 part by weight of the tuberous root with about 2% parts by weight of water, per liter of nutrient medium.

5-. A process of producing citric acid, which comprises cultivating Aspergzllus niger in a nutrient medium consisting of a sugar solution containing 14% of saccharose in addition to the inorganic salts required in a nutrient medium, to which nutrient. medium an aqueous extract of peeled sugar beets has been added in a proportion of about 0.50 liter of an extract of 1 part by weight of the tuberous root with about 2 parts by weight of water, per liter of nutrient medium.

EVERT H. GROOT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,094,023 Pollak Sept. 28, 1937' 2,415,777 Weizmann Feb. 11, 1947 FOREIGN PATENTS Number Country Date 146,430 Great Britain Mar. 24, 1921 370,039 Great Britain Apr. 1, 1933 16,651 Australia of 1928 

1. A PROCESS OF PRODUCING CITRIC ACID, WHICH COMPRISES CULTIVATING A MOLD OF THE ASPERGILLUS GROUP IN A NUTRIENT MEDIUM CONSISTING OF A SUGAR SOLUTION CONTAINING 14% OF SACCHAROSE IN ADDITION TO THE INORGANIC SALTS REQUIRED IN A NUTRIENT MEDIUM, TO WHICH NUTRIENT MEDIUM AN AQUEOUS EXTRACT OF RED BEETS HAS BEEN ADDED IN A PROPORTION OF ABOUT 0.50 LITER OF AN EXTRACT OF 1 PART BY WEIGHT OF HE TUBEROUS ROOT WITH ABOUT 2 1/2 PARTS BY WEIGHT OF WATER, PER LITER OF NUTRIENT MEDIUM. 